In order to obtain a display apparatus which is capable of producing a high definition display, various surface treatment films have been formed on the surface of the display plane of the display apparatus. For instance, the use of an anti-static anti-reflection film has been proposed, as disclosed in JP-A-4-334853 (1992). Furthermore, the use of a wavelength selective absorption film, which is capable of absorbing side bands of emission spectrum selectively, by adding coloring material for improving the color purity of an emitter, has been proposed, as disclosed in JP-A-4-144733 (1992), because the emission spectrum of the RGB emission of a Braun tube is wide and the bleeding of colors tend to occur.
One of the anti-static, anti-reflection films is formed by laminating oxide thin films having a different refractive index on each other, in order to give the film an anti-reflection effect by optical interference, and this film is mainly formed by laminating a SiO2 film as an upper layer or an ITO (InO added with Sn) film as a lower layer. Because ITO is a conductive film, the anti-reflection film itself has an anti-static effect needed. Not only the anti-static effect, but also an electromagnetic shielding function is required for the surface treatment film of a Braun tube.
One of the wavelength selective absorption films is formed by adding a reddish violet group coloring material into a thin film, in order to absorb side bands of the emission spectrum of green and red, and a Braun tube having a high contrast has been provided with such a film (Toshiba Review, vol. 45, No. 10, p831 (1990)).